We calculate the string tension, deconfinement transition temperature and bulk thermodynamic quantities of the SU(3) gauge theory using tree level and tadpole improved actions. Finite temperature calculations have been performed on lattices with temporal extent N-r = 3 and 4. Compared to calculations with the standard Wilson action on this size lattices we observe a drastic reduction of the cut-off dependence of bulk thermodynamic observables at high temperatures. In order to test the influence of improvement on long-distance observables at T-c we determine the ratio T-c/root sigma. For all actions, including the standard Wilson action, we find results which differ only little from each other. We do, however, observe an improved asymptotic scaling behaviour for the tadpole improved action compared to the Wilson and tree level improved actions.